I received a replacement for my FLT91 that was giving me problems; it was most likely a first run lemon, but the great folks at William Optics and my retailer Ontario Telescope turned it around quickly and dropped off a new FLT91 and 6AIII flattener for me to try out. Out of the box, after snugging down a few screws that were holding the focus assembly in place, I was good to go. Steve at Ontario telescopes consulted Gary Palmer who said he gap distance on the flattener/reducer must be 3.45mm for a 55mm back focus. First light image attached. I am very impressed with the optics, coming from someone who has only used the RedCat51. For this image of C34, I used an ASI294MC Pro guided by an ASI290MM and an optolong L-enhance filter. 56x180s frames under Bortle 5 skies.